1. Field of the Invention
This invention relates to a hot-water washing apparatus for personal hygiene which is used for washing the anus or the like after depositing stool in a toilet.
2. Description of the Prior Art
An example of the structure of a conventional hot-water washing apparatus for personal hygiene is shown in FIG. 1. Reference numeral 1 represents a hot-water tank with a heater 2 received therewithin and a nozzle pipe 3 connecting to a nozzle 4. One end of a suction pipe 5 having a filter 7 at its distal end is inserted into a low level cistern 6 disposed in a toilet room, and the other end thereof is connected to a vane pump 9 through a solenoid valve 8. The pump 9 is connected to the bottom portion of the inside of the hot-water tank on the discharge side by a pressure pipe 10. Reference numeral 11 denotes a vacuum breaker provided on the upper portion of the hot-water tank 1. A controller 12 controls both the number of revolutions of the vane pump 9 and the opening and closing of the closing valve 8 interlockingly when an operating knob 13 is turned and can change the temperature of hot water which is controlled by a liquid expansion thermostat 15 when a temperature adjusting knob 14 is turned. Reference numeral 16 denotes a ball tap disposed in the low level cistern 6, and 17 a static water level in the standby state.
Operation of this apparatus will be described in the following. When the operating knob 13 is turned, the solenoid valve 8 is opened and the vane pump 9 is rotated. Thereby, the washing water drawn through the filter 7 is fed under pressure to the hot-water tank 1 via the pressure pipe 10, heated by the heater 2 and the resulting hot water is pushed upward to jet out from the nozzle 4. Since the flow rate of the washing water is varied with the number of rotations of the vane pump 9, the optimum flow for a user can be selected by appropriately turning the operating knob 13.
The first thing essential to a hot-water washing apparatus in terms of the washing water supply facility is that the flow rate of washing water jetted should be appropriately adjusted, which is attained in this apparatus, as described above. The second point is that after washing, the outflow of washing water should be completely stopped. In this apparatus, when the operating knob 13 is returned to the stopping position, the vane pump 9 stops and the solenoid valve 8 is closed. Therefore, siphonal action by virtue of the water head between the static water level of the low level cistern 6 and the nozzle 4 can be intercepted, this satisfying the second point. The third point is that the residual water in the nozzle pipe 3 which has been left to cool down during the suspension of the operation should not chill the user by being jetted out at the beginning of washing. The vane pump 9 stops when washing is over and the vacuum breaker 11 is then opened because the inner pressure of the hot-water tank 1 is lowered, whereby the washing water left in the nozzle pipe 3 flows downwardly from the nozzle 4 until the water level in the hot-water tank 1 reaches the inlet of the nozzle pipe 3. Accordingly the washing water does not stay in the nozzle pipe 3 during suspension of the operation, and thus the third condition is also met. The fourth point is that it should be possible for the washing water to be fed under pressure to the hot-water tank 1, even when there is air on the suction side of the vane pump 9. That is, when a hot-water washing apparatus is newly installed or an existing hot-water washing apparatus is used when the water level of the low level cistern 6 is lower than the position of the filter 7 after, for example, the associated toilet stool has been used during suspension of the water supply, air is naturally sucked in from the suction pipe 5. Even when the water supply is recovered and the water level of the low level cistern 6 is returned, the washing water cannot flow normally downwardly due to the water head between the top of the inverted U-shaped suction pipe 5 and the water level. This example solves this problem by using a self-priming vane pump so as to utilize the suction head of the pump when air is in the suction pipe 5.
As described above, this example of the prior art satisfies the four essential conditions from the view point of the washing water supply facility. However, the self-priming vane pump, which needs to be used with variable speed, disadvantageously raises costs in terms of structure, precision in manufacturing, controlling means and so forth.
Further, a certain distance is required between the heater 2 and the inner wall of the hot-water tank 1 in order to insure safety at the time of any abnormality, such as when the liquid expansion thermostat 15 is out of order, or when the apparatus is electrically energized without water being present in the tank 1. Therefore, during heating, though the water above the heating portion of the heater 2 may be sufficiently heated, the temperature of the water between the outer periphery of the heating portion and the inner wall of the hot-water tank 1 or the water below the heater is raised simply as a result of natural convection. This hinders a uniform distribution of temperature in the tank 1, and hence leads to only a small quantity of hot-water of an optimum temperature being prepared, which leads to a rapid drop in the temperature of jetted hot water at the instant when jetting of the water in the lower temperature portion begins, even though hot water of an optimum temperature is jetted from the nozzle 12 at the beginning of washing, as is indicated by a in FIG. 5.
Furthermore, when the apparatus is actually used, further, cold water is supplied forcibly from the bottom part of the hot-water tank 1 such as to stir the hot water in the hot-water tank 1. In this way cold water bypasses the normal step, passes through the nozzle pipe and is jetted out from the nozzle 4. This lowers the temperature of the jetted hot water suddenly, even at the start of jetting. In other words, the duration of jetting out hot-water of optimum temperature is inconveniently very short.